It can be anything! An apex, subdomain, or even a URL.

Results forww25.mail.friendsofprogress.co

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2024-11-15T11:43:36.019	2024-11-15T10:45:05	2025-02-13T10:45:04	ww25.mail.friendsofprogress.co	ww25.mail.friendsofprogress.co	C=US, O=Let's Encrypt, CN=R11
2024-11-15T11:43:35.682	2024-11-15T10:45:05	2025-02-13T10:45:04	ww25.mail.friendsofprogress.co	ww25.mail.friendsofprogress.co	C=US, O=Let's Encrypt, CN=R11
2024-08-09T08:11:08.697	2024-08-09T07:12:38	2024-11-07T07:12:37	ww25.mail.friendsofprogress.co	ww25.mail.friendsofprogress.co	C=US, O=Let's Encrypt, CN=R10
2024-08-09T08:11:08.364	2024-08-09T07:12:38	2024-11-07T07:12:37	ww25.mail.friendsofprogress.co	ww25.mail.friendsofprogress.co	C=US, O=Let's Encrypt, CN=R10